1. Field of the Invention
The present invention relates to an in-vehicle input unit which is capable of operating a hierarchical menu for operating a plurality of pieces of in-vehicle equipment, using switches provided in a steering wheel, while viewing its image displayed by a vehicle display unit.
2. Description of the Background Art
In recent years, an automobile has more and more equipment on board so that safety and comfort can be improved. Specifically, an air conditioner or an audio system is provided as standard equipment, and a car-navigation system has been popular. In the years ahead, equipment related to car communication mainly including telematics, or a driving support device for adaptive cruise control system, lane keeping support system, blind spot monitoring system or the like, spreading from a luxury car to a popular car, is expected to be increasingly popular.
Conventionally, for example, in-vehicle equipment, such as an audio system, an air conditioner and a car-navigation system, which is placed in an automobile center console, needs an input unit such as a switch so that each of them can operate. In addition, each piece of equipment has a high-level function, thus increasing the number of input units such as a switch. Hence, when locating these input units for the in-vehicle equipment, a driver has to turn one's eyes away from the front visibility. This makes it hard for the driver to manipulate the input units. On the other hand, an input unit for an audio function or a driving support device is often provided on the steering wheel so that a comfortable manipulation can be realized. However, a limit is set to the number of switches which can be provided in the steering wheel. Additionally, if many switches are provided on the steering wheel, then similarly to the switching operation for each piece of in-vehicle equipment, a driver would have to turn one's eyes away from the front visibility to locate the switches on the wheel.
The specification of Japanese Patent Laid-Open No. 2001-10375 describes an improved input unit which is capable of operating a plurality of pieces of in-vehicle equipment more safely and comfortably. In this input unit, as shown in FIGS. 12A and 12B, a driver selects in-vehicle equipment, using an operation panel 110 which is provided in a center console 103. Then, while viewing a hierarchical menu displayed in a display 106 which is provided in a visible position to the driver's eyes at the wheel, the driver manipulates an input unit 105 provided in a floor console 104. In addition, as shown in FIGS. 13A to 13D, the array of the hierarchical menu displayed on the display 106 is identical with the key array of the input unit 105. If a driver touches a key, the corresponding part of the hierarchical menu on display is inverted and displayed. Thereby, the driver can execute an operation without looking at the input unit 105 as an operation portion, thus keeping the driving posture unchanged.
In the case where such an input unit is used, in order for a driver to select in-vehicle equipment, the driver at the wheel has to: turn one's eyes away from the front visibility; locate the switch of the equipment which the driver wants to operate in an operation panel provided in a center console; take one hand off of the steering wheel; and execute an input operation while driving the vehicle one-handed. This hinders the driver from driving safely. Further, when handling the switch, the driver stops gazing at a front distant spot outside of the vehicle and turns one's eyes to the switch inside of the vehicle. Thereby, the driver's eyes are focused on a short-distance spot, thus imposing a burden on the eyes. Another disadvantage also arises when the driver operates functions after selecting the equipment. The driver has to: take one hand off of the steering wheel; turn one's eyes away from the front visibility; touch a key in an input unit as an operation portion provided in a floor console; trace the selection state of the hierarchical menu which is inverted and displayed in a display inside of the vehicle; and execute an input operation while gazing at this image. This hinders the driver from driving safely. In addition, when handling the switch, from a front distant spot outside of the vehicle, the driver turns one's eyes on the display inside of the vehicle. Thereby, from the distant spot, the driver's eyes are focused on such a short-distance spot, thus imposing a burden on the eyes.